As here used, the term lubricants (often referred to also as Tubes) is not to be understood in a narrow sense and is rather intended to describe the preferred field of application. Under no circumstances is a limitation to be associated therewith, because the invention described hereinbelow can be used also with other substances that are capable of being applied to a target object by means of vapour deposition in a vacuum, including not only all kinds of lubricants and such lubricant-like materials as antiseize, slip additives, greases, parting agents or, quite generally, any kind of slip-promoting means, but also corrosion protection films, wetting agents, adhesion improvers, etc., and the term lubricant is here used in the wide sense to describe all of these, including—of course—also the preferred field of application, with a view to obtaining a slip or lubrication effect. Consequently, whenever the term lubricant is used in the remarks that follow, it is to be understood both in the narrower sense relating to the preferred field of application and in the wider sense as discussed above.
The production of (electronic) components, especially hard magnetic disks, often calls for the application of a slip layer having the primary function of assuring that friction forces on the magnetic disk will be kept as small as possible, so that the writing/reading head of a hard-disk drive can slide smoothly over the surface of the disk without thereby either damaging the disk or limiting its functionality.
The hitherto customary method for the application of slip layers of this kind envisages the magnetic disk being dipped into a bath containing the lubricant diluted in an appropriate solvent. When this is done, the thickness of the applied layer of the lubricant is set by controlling the concentration of the lubricant or the speed with which the disk is pulled out of the bath. The need for pulling the part out of the bath, in particular, may give rise to local fluctuations of the thickness of the applied lubricant. Over and above this, there is also the problem that the surface of the magnetic disk is very liable to become contaminated before it is covered with the lubricant, so that the surrounding atmosphere has to be kept as clean as possible if a utilizable layer of lubricant is to be obtained.
With a view to limiting this contamination and, more particularly, the coverage of the surface with gas adsorbates, it has been suggested, in U.S. Pat. No. 6,183,831 B1 for example, that the entire coverage process should be carried out in a vacuum. To this end several thin films are applied to an aluminum substrate in a vacuum sputter plant, the uppermost of the films being a protective carbon layer. According to the known process, the magnetic disk prepared in this manner is then subjected to the vapour deposition of a lubricant in vacuum. This is done in a vapour-deposition chamber containing a vaporization plate on which there are provided evenly distributed small storage chambers with a supply of the lubricant that is to be vaporized. The lubricant is vaporized by heating the vaporization plate, so that it enters the vapour-deposition chamber and eventually reaches the magnetic disk situated therein. With a view to obtaining an even distribution of the deposited lubricant over the disk that is to be covered, a diffuser plate is arranged between the medium that is to be covered and the vaporization plate, said diffuser plate being provided with evenly distributed passage holes. But the known process is associated with several drawbacks. Firstly, it works or deposits continuously, that is to say, the vaporization plate is used to produce a lubricant cloud into which the disks to be coated have to be inserted one after the other and then removed again on completion of the deposition. Once the lubricant has been consumed, the vaporization plate has to be dismantled and refurnished with lubricant before the process can be continued. Furthermore, lubricant is consumed even in the period between the removal of one disk and the insertion of the next. Lastly, the diffuser plate tends to reduce the deposition rate, so that the deposition period is lengthened and the process, given the low deposition rates, becomes unsuitable for mass production.